Peak dispersion in a liquid chromatography-atomic-absorption spectrometry system

Abstract

The dispersion characteristics of a flame atomic-absorption spectrophotometer, when used in conjunction with a chromatographic column and with different interfaces, were examined. It was found that the AA unit alone produces excessive peak dispersion (variance 43 µl²) and consequently, when used in conjunction with modern high-performance liquid chromatographic columns, their capabilities cannot be fully realised. The use of low-dispersion serpentine tubing, however, does permit some of the advantages of such columns to be obtained, provided the solutes are eluted at k′ values in excess of 3. It is found that the polyethylene tubing commonly used as an interface between the LC and the AA units has a variance contribution of 1.7 µl² cm^–1, which, for a practical length of 50 cm, is 83.5 µl² and consequently far too high for the efficient use of the LC-AAS system. Should modern atomic-absorption spectrophotometers be designed to provide sufficiently low dispersion so that they can be used with modern high-performance liquid chromatographic columns, then the major contribution to solute dispersion will reside in the interface and, consequently, the use of low-dispersion serpentine tubing will become essential.